C庫函數clock_t clock(void) 返回自該計劃推出以來經過的時鐘滴答數。秒使用的CPU的數量，您將需要除以CLOCKS_PER_SEC。 

CLOCKS_PER_SEC等於1000000在32位係統中，這個函數將返回相同的值大約每72分鐘一次。

聲明

以下是clock() 函數的聲明。

clock_t clock(void)

參數

• NA

返回值

這個函數返回程序啟動以來經過的時鐘滴答數。失敗時，函數返回值-1。

例子

下麵的例子演示了如何使用clock() 函數。

#include <time.h>
#include <stdio.h>

int main()
{
   clock_t start_t, end_t, total_t;
   int i;

   start_t = clock();
   printf("Starting of the program, start_t = %ld
", start_t);
    
   printf("Going to scan a big loop, start_t = %ld
", start_t);
   for(i=0; i< 10000000; i++)
   {
   }
   end_t = clock();
   printf("End of the big loop, end_t = %ld
", end_t);
   
   total_t = (double)(end_t - start_t) / CLOCKS_PER_SEC;
   printf("Total time taken by CPU: %f
", total_t  );
   printf("Exiting of the program...
");

   return(0);
}

讓我們編譯和運行上麵的程序，這將產生以下結果：

Starting of the program, start_t = 0
Going to scan a big loop, start_t = 0
End of the big loop, end_t = 20000
Total time taken by CPU: 0.000000
Exiting of the program...